define commutator and its function
Answers
A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine.
Function of commutator: To keep the torque on a DC motor from reversing every time the coil moves through the plane perpendicular to the magnetic field, a split-ring device called a commutator is used to reverse the current at that point
Commutator acts as a reversing switch. Its action in motor and generator is as below:
In case of a DC motor, commutator reverses the current (available from a DC source) at the exact instant when the armature coil crosses the magnetic neutral axis. This is necessary to maintain a unidirectional torque. Thus, the commutator converts direct current into alternating current.
In a DC generator, the emf induced in the armature coil is alternating in nature. Accordingly, the current flowing in the armature coil is also alternating current. Commutator reverses this current at the exact instant when the armature coil crosses the magnetic neutral axis. Therefore, the load (which is external to the generator) gets a unidirectional current or direct current.